薄膜外延生长的计算机模拟  

Computer simulation of thin-film epitaxy growth

作　　者：郑小平[1] 张佩峰[2] 刘军[2] 贺德衍[2] 马健泰[3] 

机构地区：[1]兰州交通大学光电技术与智能控制教育部重点实验室 [2]兰州大学物理科学与技术学院 [3]兰州大学化学化工学院

出　　处：《物理学报》2004年第8期2687-2693,共7页Acta Physica Sinica

基　　金：国家自然科学基金 (批准号 :10 175 0 3 0 );国家博士后科学基金 (批准号 :1863 7);兰州交通大学"青蓝"人才计划资助的课题~~

摘　　要：以Cu膜为例 ,用Monte Carlo算法模拟了薄膜生长的随机过程 ,并提出了更加完善的模型 .在合理选择原子间相互作用计算方法的基础上 ,考虑了原子的吸附、在生长表面的迁移及迁移所引起的近邻原子连带效应、从生长表面的脱附等过程 .模拟计算了薄膜的早期成核情况以及表面粗糙度和相对密度 .结果表明 ,随着衬底温度的升高或入射率的降低 ,沉积在衬底上的原子逐步由离散型分布向聚集状态过渡形成一些岛核 ,并且逐步由二维岛核向三维岛核过渡 .在一定的原子入射率下 ,存在三个优化温度 ,成核率最高时的最大成核温度Tn、薄膜的表面粗糙度最低时的生长转变温度Tr,相对密度趋近于 1时的相对密度饱和温度Td.三者均随入射率的对数形式近似线性增大 ,并且基本重合 .同时发现 ,随着入射率的增大相对密度不断减小 ,但是在不同温度区域入射率对早期成核率和表面粗糙度的影响不同 .当温度较低时 ,随着入射率的增大最大成核率基本不变 ,表面粗糙度不断增大 ;当温度较高时 ,随着入射率的增大最大成核率不断增大 ,但表面粗糙度不断减小 .A three_dimensional kinetic Monte Carlo technique has been developed for simulating the growth of thin Cu films. The model involves incident atom attachments, diffusion of the atoms on the growing surface, and the detachment of the atoms from the growing surface. Related effects due to surface atom diffusion was taken into account. A great improvement was made on calculation of the activation energy for atom diffusion based on a reasonable assumption of interaction potential between atoms. The results showed that as the substrate temperature is raised or the deposited rate decreased, the diffusion of particles causes the particles grouping into islands (more than three atoms). The higher the temperature or the lower the deposition rate, the larger the size of the islands. Also we observed the island shape transition from two dimensional islands to three dimensional ones. There exist three optimum growth temperatures at a given deposition rate, namely T n at which the nucleation rate is maximum, T r at which the surface roughness minimizes and T d at which the relative density approaches to saturation. They all increase with the increase of substrate temperature, and these variations almost superpose on each other. The simulation results also showed that the relative density decreases with increasing deposition rate. But the nucleation rate is close to a steadiness at a lower temperature while it increases at a higher temperature. The surface roughness increases at a lower temperature while it decreases at a higher temperature.

关 键 词：薄膜生长 Monte-Carlo算法 计算机模拟 近邻原子连带效应 脱附 

分 类 号：O484[理学—固体物理]